1. Field of the Invention
The present invention relates to an array controller for controlling a disk array made up of a plurality of disk drives and having redundancy. More specifically, the present invention relates to an array controller and a disk array-rebuilding method, which are suitably used for rebuilding a disk array by replacing a malfunctioning disk drive, which is one of the disk drives of the disk array, with a new disk drive.
2. Description of the Related Art
RAID (Redundant Array of Inexpensive Disks, or Redundant Array of Independent Disks) is known as a technology for enhancing the reliability of data by use of redundancy data. In other words, RAID is a redundant disk array comprising a plurality of disk drives. With respect to the RAID, several RAID levels are defined, such as RAID1 (mirroring) and RAIDS (striping using parity). Each RAID level is known as a technology that restores data to its original state when one of the disk drives malfunctions. Therefore, data and redundancy data are arranged in the redundancy disk array without reference to the RAID level in use.
Let us consider the case where one of the disk drives constituting a redundancy disk array malfunctions. In such a case, the disk array is rebuilt in the manner disclosed in Jpn. Pat. Appln. KOKAI Publication No. 8-221217, for example. To rebuild the disk array, the malfunctioning disk drive must be replaced with a new disk drive. Then, the array controller (i.e., the RAID controller) starts rebuild processing. In this rebuild processing, data corresponding to all areas of the malfunctioning disk drive is restored to its original state in the new disk drive. Data stored in all areas of the normally-operating disk drives is used for that data restoration. The rebuild processing restores the redundancy of the disk array. In the case of a RAID1 disk array, for example, data corresponding to all areas of the existing drives is copied to a new disk drive. Since each of the disk drives constituting the disk array has an increased storage capacity, a very long time is required for rebuilding the disk array.